Degradation of Starch–Calcium Carbonate Disposable Packaging in a Solid Waste Composting Facility

The compostability of starch–CaCO₃ disposable packaging was examined in a source-separated municipal solid waste (MSW) composting facility located in East Hampton, NY. Source-separated MSW:starch–CaCO₃ container mixtures of 0 (control), 5, and 20% (by volume) were prepared as feedstock for composting. Compost samples were collected weekly or biweekly during the composting process and examined for fragments of the starch–CaCO₃ containers. Changes in compost quality due to the presence of starch–CaCO₃ containers were assessed by measuring the nutrient and metal content of the three resultant MSW:starch–CaCO₃ composts. Finally, plant growth studies were conducted to examine the composts for possible plant growth inhibition due to the deterioration of the starch–CaCO₃ containers. Results showed that portions of the starch–CaCO₃ containers were not identified in any of the 5 and 20% sieved and characterized compost fractions > 1.3 cm following 1–3 weeks of composting. Mechanical agitation of the waste along with optimum composting conditions were sufficient to initiate the rapid degradation of the starch–CaCO₃ composites. Degradation of starch–CaCO₃ containers did not affect compost nutrient and trace element content. Grass biomass measurements were performed once weekly over 28 days for grass grown in control (0%), 5%, and 20% starch–CaCO₃-containing compost:soil mixtures. Significant differences in grass biomass for these compost:soil mixtures were measured only for the 0 and 20% starch–CaCO₃-containing compost:soil mixtures at 28 days (9.07 vs 11.05 g, respectively; P = 0.046).     

Application of Cellulose Microfibrils in Polymer Nanocomposites

Cellulose microfibrils obtained by the acid hydrolysis of cellulose fibers were added at low concentrations (2–10% w/w) to polymer gels and films as reinforcing agents. Significant changes in mechanical properties, especially maximum load and tensile strength, were obtained for fibrils derived from several cellulosic sources, including cotton, softwood, and bacterial cellulose. For extruded starch plastics, the addition of cotton-derived microfibrils at 10.3% (w/w) concentration increased Young’s modulus by 5-fold relative to a control sample with no cellulose reinforcement. Preliminary data suggests that shear alignment significantly improves tensile strength. Addition of microfibrils does not always change mechanical properties in a predictable direction. Whereas tensile strength and modulus were shown to increase during addition of microfibrils to an extruded starch thermoplastic and a cast latex film, these parameters decreased when microfibrils were added to a starch–pectin blend, implying that complex interactions are involved in the application of these reinforcing agents.     

Effects of Lime and Ash Treatments on DOC Fractions and Low Molecular Weight Organic Acids in Soil Solutions of Acidified Podzolic Soils

Dissolved organic carbon (DOC) fractions and different low molecular weight organic acids (LMWOAs) were determined in soil solutions from two lime or ash treated Norway spruce sites in the south of Sweden. At Hasslöv, 3.45 t ha^-1 or 8.75 t ha^-1 dolomite were applied 15 years before sampling. Horröd was treated with 4.28 t ha^-1 ash and 3.25 t ha^-1 dolomite and sampled four years later. Propionate (7–268 M) and malonate (2–34 M) were the LMWOAsfound in the highest concentrations at Hasslöv. Two other LMWOAs dominated at Horröd, namely citrate (18–64 M)and fumarate (5–31 M). The differences in concentration of most of the determined LMWOAs at Hasslöv were significantly increased due to treatment. The LMWOAs comprised between 1.1–6.3% of the DOC at Hasslöv and 4.5–17.6% at Horröd. At Hasslöv normally 3–10% of the total acidity (TA) was due to LMWOAs and the average specific buffer capacity was 74 ± 22 mmol mol^-1C.The total DOC concentration in the mor layer solution was 16 mM for the dolomite treated plots compared to 10 mM at the untreated plot. A major part of the increase in DOC at the treated plots apparently had a hydrophobic character and was of high molecular weight corresponding to 3–10 kDa. The concentration of DOC < 1 kDa in the control and treated plots was similar.     

Effect of OH/NCO Molar Ratio on Properties of Soy-Based Polyurethane Networks

Polyurethane networks from soybean oil have a number of valuable properties, which are determined by their chemical composition and cross-linking density. Changing the molar ratio of reacting groups can vary the latter. In this work we have varied the NCO/OH molar ratio (isocyanate index) from 1.05 to 0.40 in a soy polyol/MDI system, and tested physical and mechanical properties. The degree of swelling in toluene increased from 52–206% by decreasing isocyanate index from 1.05–0.4. The sol fractions and network densities determined from swelling in toluene were compared with ones obtained using the network formation theory based on branching processes. The comparison of experimental sol fractions and network densities with those predicted by theory of network formation suggest that 5–10% of bonds are lost in cycles and that high entanglement contributions increase the network densities. Polymers prepared with NCO/OH ratios from 1.05–0.8 were glassy while the others were rubbery, and that was reflected in their properties. Glass transition temperature (DSC) of the networks decreased from 64–7°C, tensile strength from 47–0.3 MPa, and elongation at break increased from 7–232%. The activation energy of the glass transition, determined from dielectric spectra, varied from 222–156 kJ/mol as the molar ratio of NCO to OH groups decreased from 1.05–0.4.     

Measurement of the biodegradation of starch-based materials by enzymatic methods and composting

The aim of this study was to evaluate the suitability of in vitro enzymatic methods for assaying the biodegradability of new starch-based biopolymers. The materials studied included commercial starch-based materials and thermoplastic starch films prepared by extrusion from glycerol and native potato starch, native barley starch, or crosslinked amylomaize starch. Enzymatic hydrolysis was performed using excessBacillus licheniformis -amylase andAspergillus niger glucoamylase at 37°C and 80°C. The degree of degradation was determined by measuring the dissolved carbohydrates and the weight loss of the samples. Biodegradation was also determined by incubating the samples in a compost environment and measuring the weight loss after composting. The results indicated that the enzymatic method is a rapid means of obtaining preliminary information about the biodegradability of starch-based materials. Other methods are needed to investigate more accurately the extent of biodegradability, especially in the case of complex materials in which starch is blended with other polymers.     

Investigation of Boundary Layer Fine Structure in Arid Regions: Injection of Fine Dust into the Atmosphere

Fine structure of the atmospheric boundary layerin desert regions of Kalmykia and on dried bottom of theAral Sea and its relation to soil particle emission in theatmosphere are discussed. It was found that in a hot seasonin the absence of dust storms convective processes lift updust particles into the atmospheric boundary layer fromsandy landscapes of Kalmykia and Sub-Aral regions. Thisaerosol consists of aggregate particles and contains asignificant amount of long-living aerosol of size less than5 m (including fine-dispersion 0.01–0.1 maerosol). The increasing of fine aerosol concentration wasfound at air temperature above 25 °C, surfacetemperature above 50 °C, and relative humidityless than 40–50%. Some mechanisms influencing the particle emission rates are briefly considered.     

Air Pollution Zones and Harmful Pollution Levels of Alkaline Dust for Plants

For characterisation of landscapes in north-eastern Estoniaaffected by alkaline oil shale fly ash and cement dust the zonation-method based on average annual (C _y) and short-termconcentrations of pollutants in the air was used, as well as on deposition loads of dust and Ca²⁺. In the overground layer of atmosphere the zones with different air pollution loads were distinguished. A comparative analysis of pollution zones characteristics and biomonitoring data revealed that for sensitive lichen the dangerous level of alkaline dust in the air, introducingthe degradation of Sphagnum sp. at the level of C _y of dust 10–20 g m^-3 and at 0.5–1 hr maximums 100–150 g m^-3. For Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) this limited concentration (decline of growth parameters) of cement dust is correspondingly following: 30–50 g m^-3 and 150–500 g m^-3, in case of fly ash the limit level of C _y amounting 100 g m^-3. Daily deposition load of Ca²⁺ should not exceed approximately 4.5–15 mg m^-2 for lichen; for conifers the harmful pollution load is higher – >22 mg m^-2.     

Biodegradation of an Epoxy-Based Thermoplastic Polyester, Poly(Hydroxy Ester Ether) in a Laboratory-Scale Compost System

An epoxy-based thermoplastic polyester, poly(hydroxy ester ether), was incubated under aerobic conditions in a laboratory-scale compost system for 168 days to evaluate its potential for biodegradation. Radiolabeled test polymer [uniformly ¹⁴C ring-labeled, poly(hydroxy ester ether)] was incorporated into a mature compost and a sludge-amended compost at a loading of 3 mg test polymer/g compost. ¹⁴C-Cellulose was used as the positive control and a biologically inhibited control reactor was used to assess abiotic degradation of the test polymer. Degradation of the test polymer was assessed by measuring the amount of ¹⁴C-CO₂ from each of the test reactors. In addition, at selected time intervals subsamples of the compost were collected and serially extracted with water, methanol, and dimethylformamide to monitor degradation of the ¹⁴C-test polymer and provide a partial characterization of the degradation intermediates. Extensive degradation of ¹⁴C-poly(hydroxy ester ether) was observed in the test reactors with degradation half-life of the parent polymer (t _1/2) of approximately 32 days. By the end of the study, only 2% of the total ¹⁴C activity in the test reactors was attributed to intact polymer, with most of the measurable ¹⁴C activity converted to either ¹⁴C-CO₂ (26% of total ¹⁴C activity) or nonextractable products (accounting for 60% of the total activity). In contrast to the test reactors, only 3% of the ¹⁴C-poly(hydroxy ester ether) added to the biologically inhibited control reactor was mineralized to ¹⁴C-CO₂. The results obtained from the microbially active and biologically inhibited compost systems indicate that the poly(hydroxy ester ether) polymer was degraded, at least in part, by a biologically mediated process.     

Biodegradation of Low Molecular Weight Organic Acids in a Limed Forest Soil

The effect of liming (3.45 and 8.75 t ha^-1 dolomite; 16 yr after application) on the biodegradation of three low molecular weight organic acids (citrate, oxalate and propionate) in forest soils was investigated. The concentration of organic acids in the soil solution followed the series propionate > citrate > oxalate with liming having no significant impact on soil solution concentrations (mean organic acid concentration = 8.7 ± 2.3 M). Organic acid mineralization by the soil microbial community was rapid in surface organic horizons (mean half-life for citrate = 2–6 h), with biodegradation rate gradually declining with soil depth. Concentration-dependent biodegradation studies (0 to 350 M) showed that the mineralization kinetics generally conformed well to a single Michaelis–Menten equation with V_max values following the series oxalate > citrate > propionate (mean = 9.8 ± 1.0 nmol g^-1 h^-1) and K_M values following the series oxalate = citrate > propionate (mean 168 ± 25 M). The V_max values declined with soil depth, which was consistent with a general reduction in microbial activity down the soil profile. Liming induced a significant increase in V_max for citrate with no change for propionate and reduction in V_max for oxalate. The latter was probably due to adsorption and precipitation of Ca-oxalate making it unavailable for microbial uptake. The higher adsorption/precipitation capacity for oxalate in the limed soils was confirmed by adsorption isotherms. Generally, liming increased soil microbial activity by approximately 10 to 35% with calculations based on soil solution concentrations indicating that organic acid mineralization constituted approximately 3 to 15% of the total soil respiration.     

Distribution of poly(β-hydroxybutyrate) and poly(ε-caprolactone)aerobic degrading microorganisms in different environments

To assess the capacity of the natural environment for degrading plastics, the populations of poly(-hydroxybutyrate)(PHB)-and poly(-caprolactone)(PCL)-degrading aerobic microorganisms and their ratios to the total number of microorganisms in soil samples were estimated by the plate count method with agar medium containing emulsified PHB or PCL. The numbers of the degrading microorganisms were determined by counting colonies that formed clear zones on the plate. It was found that PHB- and PCL-degrading (depolymerizing) microorganisms are distributed over many kinds of material, including landfill leachate, compost, sewage sludge, forest soil, farm soil, paddy soil, weed field soil, roadside sand, and pond sediment. Of total colony counts, the percentages of PHB and PCL degrading microorganisms were 0.2–11.4 and 0.8–11.0%, respectively. The results suggest that many kinds of degrading microorganisms are present in each environment and that specific consortia differing in biodegradation capacity are constructed.     

Fabrication and Characterization of Biodegradable Composite Films Made of Using Poly(caprolactone) Reinforced with Chitosan

Chitosan was dissolved in 2?% aqueous acetic acid solution and the films were prepared by solution casting. Values of tensile strength (TS), tensile modulus (TM), elongation at break (Eb?%) and water vapor permeability (WVP) of the chitosan films were found to be 30?MPa, 450?MPa, 8?% and 4.7?g?mm/m²?day?kPa, respectively. Poly(caprolactone) (PCL) films were prepared from its granules by compression molding and the values of TS, TM, Eb and WVP were 14?MPa, 220?MPa, 70?% and 1.54?g?mm/m²?day?kPa, respectively. PCL was reinforced with chitosan films, and composite films were prepared by compression molding. Amount of chitosan in the composite films varied from 10 to 50?% (w/w). It was found that with the incorporation of chitosan films in PCL, both the values of TS and TM of composite films increased significantly. The highest mechanical properties were found at 50?% (w/w) of chitosan content. The Oxygen transmission rate (OTR) of composite film was found to decrease significantly than PCL films. Thermal properties of the composite were also improved as compared to PCL. The water uptake test of the composite also showed promising results with a good stability of composite films. The interface of the composite was investigated by scanning electron microscopy and showed good interfacial adhesion between PCL and chitosan films.     

Photodegradation of Poly(lactic acid) Stereocomplex by UV-Irradiation

Neat poly(l-lactic acid) (PLLA) and poly(d-lactic acid) (PDLA) films and PLLA/PDLA blend films were prepared by solution casting, and their photodegradation by UV-irradiation was investigated using wide-angle X-ray scattering (WAXS), gel permeation chromatography, differential scanning calorimetry, tensile testing, and polarized optical microscopy. The PLLA/PDLA blend film was more photodegradation-resistant than the neat PLLA and PDLA films when photodegradation was monitored by molecular weight, melting temperature, and WAXS crystalline peak positions. This indicates that the chains in both amorphous and crystalline regions of the PLLA/PDLA blend film were photo-cleavage-resistant compared to those of the neat PLLA and PDLA films. The changes in melting temperature and WAXS crystalline peak positions before and after photodegradation respectively indicated the increased crystalline lattice disorder and the decreased crystalline lattice sizes of the neat PLLA and PDLA films, whereas these changes were insignificant for the blend films. Photodegradation caused no significant change in tensile properties, with the exception of significant decreases in the tensile strength and elongation at break of PLLA/PDLA blend film. However, the tensile strength and elongation at break of the PLLA/PDLA blend film retained higher values compared to those of the neat PLLA and PDLA films during photodegradation. In spite of the slower photodegradation of the PLLA/PDLA blend film traced by M _n, T _m, and WAXS crystalline peak positions than that of neat PLLA and PDLA films, the rapid decrease in tensile strength and elongation at break of the former than that of the latter should be due to the highly-ordered structural difference between them, i.e., the three dimensional dry gel of the former and the spherulites of the latter.     

A carbon-13 method for evaluating degradation of starch-based polymers

A new method for evaluating biodegradability of starch-based and certain other polymer blends uses the pre- and postexposure stable carbon isotope composition of material coupled with weight loss data to determine which components have degraded. The naturally occurring stable isotope of carbon.¹³C, is enriched in corn starch (¹³C, approx. –11) compared to petroleum-derived synthetic polymers (¹³C, approx. –32). Results on starch-synthetic polymer blends indicate that the ¹³C signatures of these blends are near-linear mixtures of their component ¹³C. Values of a ¹³C for starch-synthetic polymer blends exposed to biologically active laboratory soil and artificial seawater conditions are depleted in¹³C compared to unexposed samples, suggesting loss of the starch component. Combined with weight loss data for the exposed samples, the ¹³C values are statistically consistent with models requiring loss of the soluble component glycerin, followed by loss of starch, then petrochemical polymer, or simultaneous loss of starch and petrochemical polymer. Replicate ¹³C analyses of starch-synthetic polymer blends increase the statistical power of this relatively inexpensive, accessible technique to discriminate between degrading components.     

A Solvent-Free Approach for Production of Films from Pectin and Fungal Biomass

Self-binding ability of the pectin molecules was used to produce pectin films using the compression molding technique, as an alternative method to the high energy-demanding and solvent-using casting technique. Moreover, incorporation of fungal biomass and its effects on the properties of the films was studied. Pectin powder plasticized with 30% glycerol was subjected to heat compression molding (120 °C, 1.33 MPa, 10 min) yielding pectin films with tensile strength and elongation at break of 15.7 MPa and 5.5%, respectively. The filamentous fungus Rhizopus oryzae was cultivated using the water-soluble nutrients obtained from citrus waste and yielded a biomass containing 31% proteins and 20% lipids. Comparatively, the same strain was cultivated in a semi-synthetic medium resulting in a biomass with higher protein (60%) and lower lipid content (10%). SEM images showed addition of biomass yielded films with less debris compared to the pectin films. Incorporation of the low protein content biomass up to 15% did not significantly reduce the mechanical strength of the pectin films. In contrast, addition of protein-rich biomass (up to 20%) enhanced the tensile strength of the films (16.1–19.3 MPa). Lastly, the fungal biomass reduced the water vapor permeability of the pectin films.     

Preparation and Biodegradation of Starch/Polycaprolactone Films

Starch granules were modified with trisodium trimetaphosphate (TSTP) and characterized by P³¹-NMR, FTIR and DSC. Seventy-micron films were prepared from modified starch and polycaprolactone blends by solvent casting technique. Three different types of films—PCL (100% polycaprolactone), MOD-ST/PCL (50% modified starch and 50% polycaprolactone blend) and NONMOD-ST/PCL (50% nonmodified starch and 50% polycaprolactone blends)—were prepared, and their thermal, mechanical, and morphologic properties were investigated to show the increased performance of PCL with the addition of starch and also the effect of modification. It was observed that with the addition of starch the Young's modulus of polycaprolactone was increased and became less ductile, whereas tensile strength and elongation at break values decreased. Biodegradation of these films was inspected under different aerobic environments with the presence of Pseudomonas putida, activated sludge, and compost. It was observed that whereas P. putida had almost no effect on degradation during 90 days, with the presence of activated sludge, considerable deformation of films was observed even in the first 7 days of degradation. In a compost environment, degradation was even faster, and all polymer films were broken into pieces within first 7 days of degradation and no film remained after 15 days.     

Biodegradability: An assessment of commercial polymers according to the Canadian method for anaerobic conditions

The degradation of several biodegradable polymers was measured as a result of exposure to an anaerobic medium. The polymers investigated included materials based upon polylactic acid, polylactone, and poly(hydroxy butyrate/valerate) as well as those incorporating starch-based materials. The degradation was monitored by methane and carbon dioxide evolution. In addition, the physical and chemical changes were noted as a result of exposure. These measurements included changes in mass, dimension, and molecular weight. FTIR, UV-vis, proton, and¹³C NMR spectra were also recorded prior to and after exposure. The results clearly indicated that several biological and chemical degradation processes were occurring with the biodegradable polymers studied.Paper presented at the Bio/Environmentally Degradable Polymer Society—Second National Meeting, August 19–21, 1993, Chicago, Illinois.Issued as NRCC No. 37549.     

Biodegradation of thermally synthesized polyaspartate

Polyaspartate synthesized using thermal methods (thermal polyaspartate; TPA) has been shown to have dispersant and crystallization inhibition activities. These activities suggest that the polymer may be used in water treatment and paper processing and as a detergent and paint additive. The commercial potential for TPA is enhanced by the fact that it may be synthesized on a large scale. Therefore, a study of the biodegradation of the polymer was undertaken. TPA was produced by hydrolysis of a polysuccinimide synthesized by dry thermal polymerization of aspartic acid. The resulting polymer was a poly(,-dl-aspartate) having a 70% structure and containing a racemic mixture of aspartic acid. TPA was incubated with both dilute effluent and activated sludge from a wastewater treatment plant. Low-biomass effluent experiments showed changes in molecular size of TPA concomitant with oxygen demand induced by the polymer, suggesting susceptibility of TPA to at least partial biodegradation. Low-biomass sludge experiments (SCAS, modified Sturm) yielded approximately 70% mineralization of 20 mg L^–1 TPA by 28 days, suggesting that a significant portion of the polymer was labile. High-biomass sludge experiments using¹⁴C-TPA at 1 mg L^–1 revealed approximately 30% mineralization and 95% total removal of TPA carbon from solution in 23 days, with most of the mineralization and removal taking place in less than 5 days. Additional short-term studies using a variety of particulate substrates, including activated sludge, confirmed that TPA is subject to removal from solution by adsorption. From these studies with labeled TPA, it was concluded that TPA is subject to rapid removal and at least partial degradation in a wastewaster treatment plant. Using gel and thin-layer chromatography, it was determined that at least part of the unmineralized residue from the high biomass assays was polyaspartate. It is speculated that the unusual structure of TPA compared to natural proteins may limit the rate of proteolysis of the polymer and thus its overall degradation rate.     

An Automated Wet Deposition System to Compare the Effects of Reduced and Oxidised N on Ombrotrophic Bog Species: Practical Considerations

Critical N loads for ombrotrophic bogs, which often contain rare and N-sensitive plants (especially those in lower plant groups: lichens, mosses and liverworts), are based on very few experimental data from measured, low background N deposition areas. Additionally the relative effects of reduced versus oxidised N are largely unknown. This paper describes an automated field exposure system (30 km S. of Edinburgh, Scotland) for treating ombrotrophic bog vegetation with fine droplets of oxidised N (NaNO₃) and reduced N (NH₄Cl). Whim Moss exists in an area of low ambient N deposition (ca. 8 kg N ha^–1 y^–1), the sources and quantification of which are described. The wet N treatment system is run continuously, and is controlled/activated by wind speed and rainfall to provide a unique simulation of real world treatment patterns (no rain=no treatment). Simulated precipitation is supplied at ionic concentrations below4mMin rainwater collected on site. Treatments provide a replicated dose response to 16, 32 and 64 kg N ha^–1 y^–1 adjusted for ambient deposition (8 kg N ha^–1 y^–1). The 16 and 64 kg N ha^–1 y^–1 are duplicated with a P+K supplement. Baseline soil chemistry and foliar nutrient status was established for all 44 plots for Calluna vulgaris, Sphagnum capillifolium, Hypnum jutlandicum and Cladonia portentosa.     

Plastic shaping of aqueous alumina suspensions with sucrose and maltodextrin additives

Traditional methods for the shape-forming of engineering ceramics entail plastic deformation of powder slurries containing hazardous organic liquids as suspending media. Replacing these organic with aqueous media requires the development of environmentally benign, water-soluble additives which serve as plasticizers and binders. Fundamental studies were performed with aqueous suspensions of colloidal-Al₂O₃ to evaluate the role of sucrose and maltodextrin on viscosity, sedimentation, and filtration characteristics, plastic flow behavior of filter cakes, and sinterability. Maltodextrin systems exhibited superior results, including filtration to high packing densities and clay-like plasticity with minimal cracking.Paper presented at the Bio/Environmentally Degradable Polymer Society—Third National Meeting, June 6–8, 1994, Boston, Massachusetts.Ames Laboratory is operated for the U.S. Department of Energy by Iowa State University under Contract W-7405-Eng-82.     

Storage stability of injection-molded starch-zein plastics under dry and humid conditions

Corn starch and zein mixtures (4 : 1 dry weight) were extruded and injection-molded in the presence of plasticizers (glycerol and water). Tensile strength and percentage elongation of the molded plastics were measured before and after 1 week of storage under a dry or humid condition (11 or 93% RH). With 10–12% glycerol and 6–8% water, injection-molded plastics had relatively good tensile properties (20- to 25-MPa tensile strength and 3.5–4.7% elongation). But while exposed to dry conditions (11% RH), the molded plastics lost weight (0.5–1.5% in 7 days) and became very brittle, with significant decreases in tensile strength and elongation. Partial replacement (5–10%) of starch with a maltodextrin (average DE 5) reduced the glass transition and melting temperatures of the starch-zein mixture as well as the dry storage stability. Using potato starch instead of corn starch significantly improved the dry storage stability of the injection-molded starch-zein plastics (18- vs 11-MPa tensile strength). Anionic corn starches with a maleate or succinate group (DS<0.01) produced injection-molded plastics with improved tensile properties and storage stability. Plastics prepared from the starch maleate and zein mixture retained the strength during 1 week of dry storage without a significant change (26-MPa tensile strength and 3.7% elongation after 1 week of storage).Paper presented at the Bio/Environmentally Degradable Polymer Society—Second National Meeting, August 19–21, 1993, Chicago, Illinois.Journal paper No. J-15561 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, Project No. 2863.